oal we burn in our grates to warm us; iron, from which so many
useful things are made; gold, silver, tin, lead, and copper,--all come
out of the earth.

But these are not all the valuable things hidden away in the earth.

From salt wells we get a great deal of the salt used on our tables. From
oil wells is obtained the oil we use in our lamps to give us light.
Diamonds which sparkle so beautifully, and the stone we use in building,
are also taken from the earth.

Coal, iron, gold, silver, lead, tin, copper, mercury, and salt are
called minerals.

The opening dug in the earth from which minerals, except stone, are
taken; is called a _mine_.

One of the most useful of minerals is _coal_. Did you ever stop to think
how much hard work coal does for us? It grinds our wheat, it weaves our
cloth, it carries us by sea and by land over the earth. Hardly any labor
can be done without coal.

[Illustration: OIL WELLS.]

You have noticed that some coal burns with a great deal of flame and
smoke. That is called soft or bituminous coal. That hard, clean-looking
coal, which burns with little blaze, yet gives out such great heat, is
anthracite coal.

Coal has many uses. Mention all you can think of. From which kind is gas
obtained, hard or soft coal?

What is coal? Some day you will be able to understand how coal was made,
and how it got deep down in the earth.

What article used with food is found in mines? Does all _salt_ come out
of the mines? How is the salt made that is not found in mines?

There are salt mines where men, women, and children live all their
lives, and never see sun or sky. Many great rooms and galleries, with
tall pillars to hold up the roof, are cut out of the salt. When lighted
up with torches, they glitter as if studded with precious stones. It is
like a fairy palace.

Some minerals are called metals. Iron, gold, silver, copper, tin, and
mercury are metals.

Iron is the most useful of all metals. Did you ever think what we should
do without this hard, strong metal? The following lines tell some of the
uses of iron:

[Illustration: IRON MINE.]

Iron vessels cross the ocean.
Iron engines give them motion;
Iron pipe our gas delivers,
Iron bridges span our rivers,
Iron horses draw our loads,
Iron rails compose our roads;
Iron houses, iron walls,
Iron cannon, iron balls,
Iron lightning rods on spires,
Iron telegraphic wires,
Iron hammers, nails, and screws,
Iron every